The present invention relates to a high-voltage disconnect switch, particularly to a high-voltage disconnect switch disposed in a grounded housing filled with an insulating medium of high dielectric strength.
DE-AS No. 16 15 898 discloses a high-voltage disconnect switch disposed in a metallic housing filled with SF.sub.6 gas. Both contacts of the disconnect switch are moved by a drive to bring them into engagement with each other in one end position of the drive, and to separate them in the other end position of the drive by a gap large enough to effect a disconnect or "off" condition of the switch for a given voltage. Each contact is hollow and a contact-breaking pin is disposed in one contact and is urged in the "on" direction by a spring. A pumping device is provided in the contact in which the pin is disposed are retards movement of the contact-breaking pin to thereby delay its movement relative to the contact in which it is disposed as the switch is being switched on. After the contact-breaking pin has reached the other contact in the "on" position of the switch, the spring continues to urge the contact-breaking pin in the "on" direction and continues to do so as the contacts are started in motion to the "off" position. Since the pumping device is disposed in the contact, it is taken along therewith as the contact moves towards the off position and pumps insulating medium, particularly SF.sub.6, through the hollow contact to the tip of the contact-breaking pin so that upon the release of the other contact by the contact-breaking pin, any arc which may occur is quickly quenched by being flushed with the insulating medium. The disconnect switch disclosed in this German patent publication is therefore capable of also switching certain low loads.
Metal-encapsulated, compressed gas-insulated disconnect switches are generally equipped, for economic reasons, with a relatively slow drive for moving the contacts. Therefore, if possible, the switches are not switched under load because, if an arc occurs, the danger exists, due to the slow disconnect motion of the contacts and particularly in the case of higher voltages, of the arc travelling off the contacts and jumping to the grounded metal encapsulation, thereby forming a short to ground.